Motion blurs result from relative motion between the camera and the scene while an image is acquired. Motion blurred images can be restored up to lost spatial frequencies by image deconvolution, provided that the motion is shift-invariant, at least locally, and that a blur function, also known as a point spread function (PSF), that caused the blur is known.
Maintaining invertible motion PSF is not possible in conventional images. A box function due to a finite exposure time corresponds to a convolution with a low pass filter, and hence a frequency transform of the PSF contains zeros (nulls). The frequencies corresponding to the nulls of the PSF are lost, which makes the deblurring ineffective. Conventional methods use specialized cameras to determine the PSF.
For example, one conventional method opens and closes a shutter during an exposure time using a broadband binary code. The broadband code does not have any nulls in the frequency domain, thereby making the resulting PSF invertible. However, that method requires specialized hardware, assumes a constant background, and requires a manual PSF estimation and object segmentation.
A motion invariant imaging method moves the camera with a constant acceleration while acquiring the image. The key idea is to make the motion PSF invariant to object velocity within a certain range. This makes segmentation and PSF estimation unnecessary. However, that method requires a prior knowledge of the direction of the motion, creates artifacts at object boundaries due to occluding background, and critically introduces blur even in the static parts of the scene.
A wavefront coding method uses a cubic phase plate in front of the lens to make the PSF invariant to scene depths. However, that method results in defocus blur on scene parts originally in focus.
Another method open and closes the shutter of the camera with a broadband binary code to make the PSF invertible. Accelerating camera motion makes the motion PSF invariant to the velocity of the object, at the cost of blurring static parts.
Conventional consumer cameras perform image stabilization using adaptive optical elements controlled by inertial sensors to compensate for camera motion.
A hybrid Camera uses a hybrid imaging system that estimates the PSF using an auxiliary low-resolution high frame rate to deblur the high resolution primary sensor images. However, that method requires an auxiliary camera for PSF estimation.
Motion PSF has been estimated by combining partial information from successive images having two different exposures: a short exposure for PSF estimation and a long exposure for an image deblurring using the estimated PSF. However, a special camera is required for acquiring the image with a short exposure.
Multiple co-located cameras with overlapped exposure time and reconfigurable multi-camera array have also been used to increase the temporal resolution of the acquired images. However, it is desired to use a single conventional camera for PSF inversion.
It is therefore desired to deblur of a scene even if the PSF of each image is non-invertible due to a blur, and the images are acquired by a single conventional camera.